Impostor
by Invader Snik
Summary: After spending the morning building a tesseract, the boys decide they want to build an incarnation of a robot rhinoceros game they've found on the Internet. There's only one problem. Phineas seems to be acting a little...strange...
1. Exposition

**Obligatory disclaimer: the character of Marissa Flynn belongs to "iheartphinabella05" but all other OCs are mine.**

**A/N: this is my first full-length fic so the only criticisms I will accept will be of the constructive nature (as if I would settle for less than that in the first place). Although all of my fics will be published as separate stories (except for a select few that will have specific sequels) it is recommended that they be read in order, since a few minor OCs will appear in future fics.**

Impostor

Chapter One: Exposition

Ferb

"Hey, Phineas. What'cha doin'?" Isabella's voice chirped and she rocked back and forth on her feet as she asked her signature question. She had her hands neatly behind her back and blinked sweetly at my step-brother.

"Oh, hi, Isabella," Phineas replied, poking his head out from behind our latest half-built machine. He glanced at the wrench in his hand and dropped it in the toolbox. "We're building a tesseract."

"Oh, okay," Isabella frowned a little, then added, "What's that?"

"It's an octachoron," I supplied, "Like a cube is three-dimensional, a tesseract is four."

"Oh! I get it! That's cool!" Isabella grinned cutely and then lingered on Phineas for a few moments longer than was necessary.

Phineas didn't seem to notice. He never did. Instead he just tipped the tesseract on its side and continued work. After a minute he looked up and asked, "Hey, Isabella, could you do me a favor?"

"Sure!" she squealed, "What do you need?"

"Just a couple of odds and ends from the hardware store," he handed her a short list and she happily skipped off to complete her task. She began singing to herself, but her voice quickly faded and she was gone.

I turned back to Phineas, taking a look at the pieces of the tesseract that he had been working on. This was by no means the biggest or most extravagant thing we'd created-more of a mind teaser than anything, really-but it had been on my to-do list for a small while and Phineas finally agreed to help build it.

"Hey," Phineas suddenly stopped and took a look around. He turned to me and frowned. "Where's Perry?"

I just shrugged.

There was a sudden scream from inside and we both cringed. That would be Candace. She stormed outside, barefoot, and gave each of us an angry glare. "Okay, which one of you geniuses put spiders in my shoes?"

I looked over to see that Phineas was doubled over with laughter. After a minute he calmed down enough so he could speak and then said, "That would be me-" and then he burst into a new wave of giggles, tears now running down his face.

Candace gave him a furious look and then stomped back into the house. After a moment she poked her head out the door and declared, "And whatever crazy thing it is you guys are building today, I'll find out and you'll both be busted!" and then she was gone.

There was the distinct sound of the backyard gate swinging open and Phineas and I both turned to see Moon leaning against the fence. We hadn't spoken since she'd first come to Danville the week before-that's another story-but I knew she had taken residence on that creepy house on the end of the block. For now she just said, "Sup."

"Oh, hey," Phineas grinned, "What's up, Moon?"

"Can I have a nap in your tree for a few hours?" she inquired, "All my trees are dead so the sun keeps getting in my eyes."

"Umm...okay..." Phineas gave her an odd look but didn't press the matter any further.

"Thanks," Moon jumped quickly into the tree and disappeared into the leaves, out of sight of the both of us.

Phineas turned to me. "Well, that was weird."

Just then Isabella flounced into the backyard, holding a bag of assorted parts from the hardware store. "Here's that stuff you needed," she offered to Phineas.

"Thanks, Isabella," he took the bag and then added, "But could you keep it down just a little?"

"Why?"

"Moon fell asleep in the tree and we don't want to wake her up," Phineas gave Isabella an understanding grin.

"Oh..." Isabella's face hardened and she gave Phineas a flat look. Her dislike for Moon was obvious in that and I was beginning to think she would never come to like her at all.

"Wait, what about the moon?" we all turned to see Marissa walk out onto the lawn holding a half-eaten piece of toast in one hand.

"You remember that one time last week when you and Candace and Mom and Dad came home from that weird parent-daughter thing you went to and I told you we raised the dead by accident?" Phineas asked.

"Yeah," Marissa nodded, "Go on..."

"Well, Moon saved us-"

"Yeah, after she tried to strangle you to death," Isabella interrupted, accompanied by a roll of her eyes. She crossed her arms and then added, "Seriously, Phineas, how do you keep forgetting that?"

"Well, it _was_ just a misunderstanding," Phineas shrugged.

"Wait, she tried to _what?_" Marissa exclaimed, her eyes widening, "What, is she a psycho-killer?"

"Well, kinda...more of a zombie enthusiast, really," Phineas put in.

"No," Marissa shook her head, "I will not have anyone dangerous hanging out around my brothers," she crossed her arms and headed over to the tree where Moon was sleeping. She looked up into the leaves and said, "Hey! Moon!"

There was no answer. A slight breeze rustled the leaves but that was all.

Marissa began tapping her foot irritatedly. "Hey! I'm talking to you!"

Suddenly Moon came, falling without a sound but landing with a soft thud on her feet behind Marissa. She was dressed in what I assumed to be her standard: black midriff tank-top, loose grey jeans with an extra pocket on one side, and a thin silver belt holding a dagger with a tiger's-eye hilt. She went barefoot and, although I couldn't see it from here, I guessed she was wearing her little choker pendant as well. Her messy brown ponytail cocked to one side as she seemed to size up Marissa. After giving her a completely blank look she spoke. "You must be the big sister," she said, "Candace, I presume?"

"Marissa," Marissa said shortly, "Now what's this I hear about you trying to kill my little brother?"

"Pardon?"

"Isabella said last week you almost strangled him to death!" Marissa exclaimed, giving Moon a glare more angry that Candace had been about the spiders.

"I'm over it," Moon shrugged, "Not like I succeeded anyhow."

I was about to say something about how that probably wasn't the best sort of remark but Marissa was quicker and responded with an enraged look. "Now see here, you. If you _ever_ lay a hand on my brothers-"

"Whoa, Marissa!" Phineas intervened, "Calm down! Don't be so mean; Moon's our friend now."

Marissa softened. After a minute she sighed and said, "Well, okay...but you be careful around her, Phineas."

"Whatever makes you happy, sis," Phineas grinned disarmingly at her.

Marissa seemed satisfied with this answer and then turned back to Moon, who was leaning against the tree with her arms crossed neutrally. "You better not touch my brothers," she warned, with her protective sister-bear stare.

"The thought," said Moon, "Hadn't even begun to speculate the merest possibility of crossing my mind."

Something in the way she said that told me she might not be taking Marissa very seriously. After all, Moon was easily a year older than Marissa was; she would probably be able to take Marissa down in any sort of fight (not that I would wish that to happen, of course).

Marissa turned without another word and went back into the house-I assumed it was to get another piece of toast since the one that she was holding was now gone.

Moon didn't seem to care. Instead she just yawned-she reminded me a little of the neighbors' cat in doing so, actually-and ambled over to where Phineas and I were working. "What is that, a tesseract?"

"Yeah," Phineas nodded, "Ferb's idea."

"That's nice and all," Moon commented, "But isn't it a little impossible?"

"That is a possibility," Phineas looked up at her and shrugged.

Isabella, who had been watching until now, spoke up. "You're obviously new to the neighborhood," she sighed as she gave Moon an unimpressed look. "We do the impossible all the time."

"I see," said Moon, in a tone that heavily implied that she didn't like Isabella either.

"Aha! Got it!" Phineas announced happily as he turned the tesseract right-side-up again. It wasn't a _real_ tesseract quite yet, as it hadn't become four-dimensional, but in a minute it would be. Phineas gave me a small remote with a single button on it and said, "Ferb, since this was your idea, care to activate it?"

I took the remote and pushed the button. Instantly there was a small *click* from inside of it and I knew it was now four-dimensional.

"Success!" Phineas exclaimed, giving me a solid high-five. He picked it up and darted inside to put in our room, disappearing through the door and out of sight.

"Well, that was interesting," Moon said, jumping back into the tree, "But I'm going back to sleep."


	2. Suspicion

**A/N: as promised, the second chapter of **_**Impostor...**_**I'll hopefully be putting up the next chapter sometime this weekend, if I can, or else early next week. Any sort of constructive criticism is greatly appreciated so please review, and enjoy...**

Impostor

Chapter Two: Suspicion

Isabella

I watched Phineas run into the house with the tesseract. I'll admit it wasn't as cool as I was hoping for. Even after being activated, it was still just a box. Kinda disappointing. That said, it had taken less than an hour to build so there was a good chance they'd think of something else to do. Hopefully I could get in on some of that too. I sighed contentedly about half a second before Phineas came back outside. He took a quick glance at the sun and then frowned. "Well, that didn't take long. You wanna hang around for a while, Isabella? Maybe we'll figure out something _else_ we wanna do today."

"Sure!" I grinned, not only because I had predicted this would happen but because it meant I got to spend time with Phineas...ahh...

"Great!" Phineas took his usual morning-spot under the tree and Ferb and I joined him. It was actually pretty nice and quiet. The three of us, sitting there, in the shade...

I scooted a tiny bit closer to Phineas. When he didn't notice, I scooted a little closer again.

Ferb seemed to take the hint and quickly excused himself.

I looked over at Phineas. He had his hands laced behind his head in a relaxed pose and was staring off into space. I inched closer still to him and watched to see his reaction.

Phineas sighed. "Isabella, could you move over, please?"

"What?" I stalled. This had not been what I was hoping for.

"Move over," he repeated, "Your breath smells like cereal and it's kind of annoying."

"Eep!" both of my hands immediately flew up to my mouth and I shrank back, too embarrassed to do anything else. I could feel my face turn a bright pink and I quickly turned away from him so he wouldn't see. "Sorry."

"S'fine," he shrugged, without taking his eyes off whatever he was staring at. "If it was bacon I wouldn't have had a problem."

"Hey!" I frowned, turning back to him, "Phineas, you know I'm Jewish-"

"Oh, right," he said quickly, "Sorry, forgot."

I gave him an annoyed look, crossing my arms. "_I _wouldn't forget if it was _you_."

Phineas seemed like he was about to rebut, but the back gate opened and Ginger poked her head in the yard. "Guys," she said, a little quietly, "Have you seen Mister Squiggle Muffin?"

"What?" both of us asked together.

"He's my new bunny," Ginger explained, "We just got him yesterday. I didn't train him yet and this morning he got out of his hutch. Can you please help me find him?" she handed me a picture of the rabbit-cutest little grey-and-brown bunny I'd ever seen-and then added, "I told the other Fireside Girls about him already. They said they're looking for him, but I'd really appreciate your help."

"No problem," I told her confidently, "We'll keep an eye out for Mister Squiggle Muffin."

"Thanks, guys," Ginger said appreciatively, then closed the gate behind her as she left.

Just then Ferb returned with a box full of what I assumed were blueprints and me and Phineas both looked up. He dropped the box with a thud on the ground in front of Phineas and they both began going through them. Phineas finally held one up to me and said, "Hey, Isabella you think this would be a good idea for today?"

Before I could answer, there was a distinct _plunk_ as Phineas was hit on the head with...an onion? I picked it up after it came to a stop at my feet, giving it a quizzical look. Where had this just come from? I knew the neighbors had planted a few onions, but-

Just then a beet came flying over the fence and nearly hit me, landing less than a foot in front of me. What in the world...? As if chasing the onion and the beet, several dozen other assorted fruits and vegetables followed, scattering across the grass in front of us. The last to go was a small watermelon, landing squarely on the top of Ferb's head. He swayed back and forth for a moment before shaking the dizziness out of his head and giving the both of us a thumbs-up.

"What is going on over there?" Phineas asked, jumping up the side of the fence to get a peek. Ferb and I joined him.

The garden that usually sat in the corner of Missus Hirano's yard was now torn up, clumps of dirt flung around the area as if some wild animal had been trying to tunnel to China. In the middle sat Moon, clawing away at a little hole in the ground.

I knew she was trouble.

"Um, Moon," Phineas asked, "What are you doing?"

Moon jumped. She turned to Phineas and answered, "Catching lunch."

"In Ginger's mom's garden?" I protested.

"Well, there doesn't seem to be anyone home to notice," Moon turned and glanced at the house. I knew the Hiranos (with the exception of Ginger, of course) were out of town for the day, but I wasn't about to tell Moon that. She obviously didn't need my encouragement to find trouble. Instead I said, "You know, Moon, I don't think that-"

"Aha!" Moon suddenly pounced, catching in both hands what I thought was some sort of rat. I couldn't quite see it and besides, it was squealing really loud. Moon held it up triumphantly and I identified it as the rabbit Ginger had lost this morning. Before I could say anything, Phineas spoke up. "Hey, isn't that Ginger's rabbit?"

Moon held the rabbit behind the neck with one hand and turned back to Phineas. "What?"

"Ginger came by a few minutes ago asking about her missing rabbit," Phineas told her, "I think that's it."

"Wait a minute," Moon frowned, "_I_ get to eat it-I caught it."

"No way!" I exclaimed, "How could you do that to that cute little bunny?"

Moon rolled her eyes at me. "Well, it's made of meat, for one..."

"Moon, can Ginger have her bunny back?" Phineas asked, giving her a hopeful look.

Moon sighed. "Fine..." she dropped the bunny into his arms and then said, "But lunch is on you guys today."

"I'll take Mister Squiggle Muffin back to Ginger," I offered, taking the rabbit (which I'm pretty sure had no idea what was going on, nor seemed to care) and heading out the back gate. I could hear Phineas' voice trailing off as I headed down the street: "You know, Moon, you really don't have to hunt for food anymore..."

I didn't like that Moon. She was just so _weird_. Phineas had told me that she'd been traveling for years and regularly hunted for herself, but I still didn't see why she would just go after that cute little bunny like that. Some sort of vermin, like a rat or something, but not a bunny-rabbit. I was just glad she gave it back. I'd have been so mad if she would have killed him.

I spotted Ginger across the street and called, "Hey! Ginger!"

She turned. Instantly she brightened and declared, "Mister Squiggle Muffin! You found him!"

"Yeah, he was hiding in Phineas' garage," I lied. I didn't want to give Moon any sort of credit, since she'd almost killed the bunny and I knew Ginger wouldn't want to hear about that.

"Aw," Ginger took Mister Squiggle Muffin and headed back to her house and I turned back to Phineas' backyard. I opened the gate and saw that he, Ferb, and Moon were sitting under the tree around a pile of the assorted vegetables that had been thrown over the fence. The watermelon had been chopped open and Moon was eating that. Ferb was in the middle of a small pile of crabapples and Phineas was chewing on a-zucchini?

"Phineas," I said as I approached him, "Are you eating a zucchini?"

Phineas looked down at the half-eaten thing in his hand and frowned. "Oh, is that what this is?"

"You hate zucchini," I told him, "You said so yourself, it's got 'ucch' in the name."

"It's not that bad," Phineas shrugged, "A little squishy, perhaps..."

It was then that I realized something was wrong. I didn't yet know what it was, but I knew it was something. I could feel that tingly feeling going down my spine-it wan't fear, exactly, but that sudden realization...I tried to ignore it. I told myself it was nothing. Phineas was okay. But I still found myself asking. "Phineas...are you feeling okay?"

"Peachy," he assured me with a smile, "Why do you ask?"

"Well..." I started, then quickly decided against it. I was being irrational. This was nothing. Jeez, Isabella, get over yourself. There was _nothing_ wrong with Phineas...was there?

"Well," Moon said, having finished the watermelon, "I'll catch you guys later," she stood up and then left, doing a quick parkour over the fence on her way out.

As if it had been waiting for this moment, a folded paper envelope fell seemingly out of nowhere and landed in my lap. With curiosity, I picked it up and glanced around. Phineas and Ferb had taken to shuffling through the blueprints again and there was nobody else around that could have given this to me. This was weird. Uncertainly I began unfolding it. When I saw what was inside I gasped.

It was a pencil-drawing of Phineas. It was almost as if someone had taken him and pressed his essence onto the paper-almost. His smile was perfect, his arms crossed in a casual stance, leaning up against the tree that I was sitting under. Only one thing about him was different: his eyes. Instead of the cool blue that they normally were, they looked in the drawing like they had been ripped out and replaced with the eyes of some horrible monster. They were completely void of color, blank grey-white circles almost reptilian in nature-and they were staring at me. I could almost see this drawn Phineas-monster laughing at me, mocking me with the ugly brutality his new eyes gave him. I could feel the tingle go again down my spine as my eyes fell to the bottom of the page. There was a single word, scrawled in all capital letters: IMPOSTOR.

I tried to keep my hands from shaking as I looked up at Phineas, who was holding two blueprints up to Ferb.

Or was it even Phineas at all...?


	3. Investigation

Impostor

Chapter Three: Investigation

Candace

"So then Stacy was all like, 'well I don't even like Robby anyway,' and I was all like, 'oh-magawd, Robby is soooo cute,' but not cute like Jeremy, 'coz Jeremy's like the cutest guy ever, and then-get this-Stacy said-"

"Candace! Candace! _Candace!_" there was a frantic voice from outside the door and I groaned. "Go away, I'm in the middle of a conversation here!"

Marissa, who had been sitting cross-legged on the floor listening to me, gave me a sour look. She stood up and opened the door and no sooner than that Isabella ran into the room, holding a crumpled piece of paper in one hand. Her face was pale and tears had begun to well up in her eyes.

"Isabella," Marissa gave her a look that was both surprised and concerned, "What's the matter?"

"It's Phineas," she said through her tears, "He's-"

"Busted!" I cried, darting over to the window to see whatever it is they were building. Every day it was something and it was always bust-worthy-well, except for that one day when they didn't do anything-so I knew I would catch them in the middle of a project. I was right! It didn't look like anything in particular right now, but there were trucks dropping off supplies and equipment and stuff in the backyard and I could see a set of blueprints in Ferb's hand. "Aha! I knew it!"

"Listen," Isabella said quietly, "That's not Phineas."

"Pfft, yeah, right," I rolled my eyes at her and then turned back out the window. "What, did they build brobots again?"

"Candace, listen to me!" Isabella demanded. She gave me a narrow-eyed glare and stamped her foot, curling her hands into fists. She shoved the paper into my hands and then told me, "That's not Phineas out there!"

"What are you talking about?" I un-crumpled the paper to find a doodle of Phineas, except with weird bug-eyes drawn in. "What is this, some sort of joke? Are they building bug people today or what? That's it!" I turned back to the window and looked closely. No. It was still too early to tell for sure. But given ten minutes- at most-it would be easy to see what _exactly_ was coming together in the backyard. These things had a rhythm to them and by this time I knew it well-perhaps too well. By noon they would have it finished and by the time Mom came home it would be gone. It always was. But that wasn't about to stop me. Oh, no...one day I _would_ bust them. Both of them. I narrowed my eyes in determination as I watched Ferb direct a truck full of boxes out into the yard.

"Candace," Marissa's voice was thin and I could practically hear her staring at me. I groaned. Marissa was known to take everything too seriously-especially when it came to her brothers. She was kind of disappointing that way.

I turned to see her with her arms folded, giving me a "just-hear-her-out" kind of look. I retorted with my own look, the kind of look that says, "oh, right, like I really want to listen to whatever crazy thing it is that's gonna come out of Isabella's mouth." I then turned back to the window to see if they actually _were_ building bug people.

I thought it likely.

"Candace, you don't understand," Isabella exclaimed, "That's not Phineas out there. That's-"

"Yeah, yeah, whatever," I shooed her off with one hand and then gave her an annoyed look. "Bug people and all that. But I don't need your help to bust them. I can do it by myself. Just you wait and see. Now go away-there's busting to be done and _I'm_ the one who's gonna be doing it!"

"But-"

"I said get out of here, I'm busy," I turned and pushed Isabella and Marissa out the door. I knew that they could only be a distraction. I had so much busting to do...so much. I could hear them grumbling to each other but I paid it no mind. Instead I turned back to the window in time to see Phineas finish welding two enormous pieces of pipe together. He had the blueprints for the project in front of him and glanced back at them for reference, picked up a smaller piece of pipe, and began welding that too.

Nope. Still too early to tell what it was. I sighed. Just then my cell beeped and my eyes lit up. It was Stacy, of course. I wondered why she hadn't called earlier and so I was eager to talk to her; Marissa was fine and all but Stacy was much more understanding. I dug the phone out of my pocket and answered. "Hey Stacy."

"Candace, you're not going to believe this!" Stacy sounded overly excited and I knew that if she was excited I would probably get excited about it too.

"What is it?" I asked.

"You know that kid Coltrane that lives two blocks from your house?"

"Yeah, that semi-cute one?"

"Yeah he just said I was cool!"

"Eek!" I squealed, instantly smiling.

"I know!" Stacy agreed, her voice high-pitched in excitement.

"So what did you say, after that I mean?"

"I said cool," Stacy replied, "I mean like I didn't wanna sound too clingy about it, right, but I didn't wanna be all cold and distant-"

"No Stacy that was totally fine," I assured her.

"Kay," she sighed, "I was kinda worried for a minute coz what if I handled it wrong, you know?"

"Stacy, relax, you're fine."

"Thanks, Candace."

I was about to make another comment, but there was a spectacular crash from outside. It sounded like something very big had been dropped from a very high place and had landed on another very big thing.

I huffed in annoyance. "Stacy," I said, "I'll call you back."

"I get it," Stacy sighed, "Busting time?"

"Busting time," I snapped the phone shut in annoyance and stomped out the door, arms crossed. "Okay, you two, what kind of chaos is it this time?"

"Oh, hey, Candace," Phineas greeted happily, jumping down from what looked a little like the horn of a monstrous unicorn. "We're building a track for _Attack of the Robot Rhinoceros_. You know, that online game we showed you yesterday?"

I rolled my eyes in disgust. "What. Ever."

"Suit yourself," Phineas shrugged, "But at the rate you're going you're never gonna get to see it, let alone have a turn."

"What?" came Marissa's voice from behind me. "Of course she can have a turn, Phineas."

"With her attitude?" Phineas asked, giving her a skeptical look.

Marissa looked like she was about to snap at him-which I'd never seen happen before, by the way-but instead turned to me. "Candace, you mind coming inside for a minute?"

"More than a minute," I nodded, then turned back to the boys. "I'll see you two weirdos later."

"C'mon," Marissa quickly led me inside and up to her room closing the door behind us. Isabella was there too, sitting quietly on the bed. She didn't say anything, of course-the expression on her face made it clear she had been crying.

Marissa sat next to Isabella on the bed and then turned to me. "Sit down."

I took a seat on the purple bean-bag chair in the corner. "What is it?"

Marissa sighed. "Candace, we need your help."

I scoffed. "Help with what?" I asked, crossing my arms, "Does Phineas not get hugged enough?"

"Candace," Isabella snapped, "Just shut up and listen."

"Fine," I sighed.

"Okay. So. Phineas has been acting weird all morning. Tell me you've noticed that," Marissa looked up at me with hopeful eyes.

"What do you mean weird?" I asked skeptically.

"I mean weird as in he _ate a zucchini by himself_," Isabella exclaimed, "That's not normal!"

Marissa gave me an "explain-that" look, crossing her arms.

"Are you kidding, there is _absolutely_ nothing wrong with zucchini," I protested, "They're just vegetables."

"Yeah? and how about this?" Isabella demanded, again showing me the Phineas-bug-eye doodle.

"What about it?"

"Hello, this is obviously not Phineas!" Marissa exclaimed. She was on the verge of true anger, and yet it was obvious she was picking out convenient details out of the picture-and I knew all about that; I'd done it myself a few times in the midst of the Busting.

"And what's that supposed to mean?" I snapped.

"Argh!" Marissa shouted, exasperated, "What do we have to say to make you listen to us?"

"Maybe _nothing_ because what you're saying _doesn't make any sense!_" I shouted, "Jeez!"

"Ah!" Isabella exclaimed, apparently having some sort of idea, "What about this. You go and do your thing and see for yourself."

"What?" I asked.

Marissa clarified: "Bust 'em."

On the word _bust_ I was immediately paying attention-like some sort of trained monkey or something. Against my better judgment I inquired further. "Lemme get this straight. _You're_ telling _me_ to bust my brothers?"

"Yes," Marissa confirmed.

"What's the catch?" I asked skeptically.

"No catch," Isabella shook her head, "Just...bust 'em."

"Hmmm..." I knew I had to think this over. Something just smelled fishy about it. It occurred to me that the boys may have put her up to this, to keep me off their back for a while-I bet they were counting on me knowing something was up so then by busting them I would not be busting them and by not busting them I would be busting them! Aha! I had it! If busting meant not busting and not busting meant busting, then busting was busting whether they wanted me to or not! "I got it!" I shouted triumphantly, "I will bust my brothers!"

"Yes!" Isabella cried, "Bust 'em!"

"Yeah!" now all fired up and determined to catch them at whatever it is they were doing, I ran back to my room to take some serious notes. It looked like they had the track for the robot rhino almost done, but there was no robot rhino...hmm, this was suspicious. It was almost lunchtime-they were always done by lunchtime. I spotted Phineas going over the blueprints with Ferb and watched carefully. They seemed to have a disagreement over some small part of it, and Phineas finally stomped off. What? That never happens. Phineas and Ferb always finish before-

"Lunchtime!" I heard from downstairs. Yep. That. I sighed, coming downstairs for the lunch that was announced. I gave the boys an annoyed look as Dad gave us each a sandwich and then went back to watch TV.

"What do you want, Candace?" Phineas asked, returning my look with one of his own.

"Oh, nothing," I replied, refusing to break the gaze. "Just nothing."

Phineas shrugged and then went back outside to work some more on the robot rhino. Ferb hesitated a moment, but then followed.

This was officially weird. The boys weren't done yet. Something had to be wrong.

I had to do some serious investigation.


	4. Proof

Impostor

Chapter Four: Proof

Marissa

"You know she's gonna find _something_," Isabella told me, "She's Candace. She takes her busting very seriously."

I sighed. "I know, but I'm just worried, that's all. You know me, always looking out for my brothers."

"Yeah," Isabella's voice trailed off and she looked down out the window. The boys were sitting over the blueprints and seemed to be discussing some design flaw or other. She sighed, turning back to me. "What if Candace doesn't find anything? What if I just imagined it?"

"I believe you, Isabella," I told her, giving her a reassuring smile.

There was a quiet knock on the door and Isabella jumped off the bed to go and open it. On the other side stood Ferb, holding the rolled-up blueprints for today's project. Although he kept his blank-faced look I could tell he was worried about something. Before he could say anything Isabella gave him a look. "It's Phineas, isn't it?" she asked.

Ferb only nodded.

"Candace is on it already," Isabella told him, "Soon as we hear back from her-"

As if on cue Candace burst into the room, accidentally knocking Ferb over and giving me a panicked look. "Ohmygahd, guys, you're not gonna believe this!"

"About time," Isabella crossed her arms at Candace in a clear expression of annoyance. After a moment it was replaced with urgent concern and she asked, "So what did you find?"

"Come and see," Candace took Isabella's arm and we all followed her back into her room, where she had a tripod set up overlooking the backyard. She had the camera resting on the bed, paused at a certain point, and she turned it so we could all see. "Look at this," she said, pressing the _play_ button on the camera. Since the footage had been taken from the window, there was no audio, but it was clear that Phineas was in the middle of screwing two pieces of metal together. After he finished he picked it up and looked at it for a minute, frowning, and then turned to refer to the blueprints. He briefly turned back to the part he had put together, and then again to the blueprints.

"There!" Candace cried as she paused the footage and pointed to the screen on the camera. "You see it?"

"No," Isabella admitted, "What is it we're supposed to be seeing?"

"Right here," she backed it up a few seconds and then played it again, this time frame-by-frame. Slowly we watched again as Phineas turned to the blueprints. As he turned back, I could see his eyes had changed-into what Isabella had found earlier this morning.

Isabella gasped, also seeing the change, and Candace paused the video. "See," she said, as if this was her idea in the first place and we didn't already know about it. "I told you there's something wrong here!"

"Um, Candace-" Isabella started.

"I _so_ told you," Candace ignored Isabella completely and gave us each a brief triumphant look.

"Candace," I snapped, "Pay attention."

Candace frowned at me but she didn't say another word. Instead she just crossed her arms.

"So what do we do?" Isabella asked, "I mean, did Phineas get turned into a monster now or what? and how do we turn him back?"

As if there had been any question before, I now knew that this wasn't Phineas. _Some_thing had taken him and I wasn't going to stop at _any_thing to get him back. Only thing was...I didn't know how to do that. If only we could find out about whatever kind of monster it was-maybe Baljeet would know. It was worth a try, at least. I spoke up: "We could ask Baljeet. He's bound to know _some_thing."

Isabella was about to say something, but Phineas's familiar voice came from the doorway. "Hey, Ferb."

I turned to see the impostor leaning against the doorframe. Its arms were crossed and it gave Ferb an annoyed look. "Ferb, I told you to bring out those jumper cables like ten minutes ago. Now come on, get your head out of the clouds-we have stuff to do."

Ferb just looked helplessly at me, but then turned and followed Phineas out the door. I was about to protest, to tell that monster _exactly_ what I thought of it, but Isabella grabbed my arm and pulled me back. She shook her head-now was not the time. Realizing this, I nodded; we didn't really know what it could do, and I didn't want to take any chances. Instead, we just waited till they were out of earshot and continued the discussion.

It was half an hour later and we had decided on a course of action. I was at Baljeet's house, waiting for him to answer the door, and once we got some info on this monster we would figure out how to destroy it and get my brother back. I worried for him, taken away to some horrible place. He must be so scared, all alone-it suddenly struck me that there may be more of those monsters, perhaps a pack of them, and the rest were keeping Phineas away from us. But why? Why would anyone take my little brother? What could they possibly want with him? That was what worried me the most. I only hoped that he wasn't hurt, or...it pained me to even think it...dead...

Baljeet opened the door and then looked up at me. "Oh," he said, "Hello, Marissa. What brings you here?"

"Baljeet, we need your help," I told him, "Phineas has been kidnapped by a monster and we need to know what it is."

"Phineas? Kidnapped?" Baljeet exclaimed, "Oh, that is terrible! I will do anything I can to help you."

"Great. I need you to find out as much as you can about anything related to this," I handed him a snapshot of the monster-one of the few frames that Candace had caught with the freaky eyes that had given the monster's secret up. "Let us know as soon as you find anything."

"Okay," Baljeet said, taking the picture, "Give me half of an hour, and I will give you everything you need to know."

"Thanks," I said, relieved. It had occurred to me earlier that Baljeet might not have the info we needed. But then I remembered his nickname of "human encyclopedia." Of course he would be able to help. He'd probably throw in some unrelated math facts too. I headed back home, careful to avoid the backyard, and quickly went inside, up to Candace's bedroom. She and Isabella were there, keeping a close eye on the impostor to make sure nothing happened to Ferb. Isabella turned to me as I opened the door and asked, "So?"

"Yeah, he's on it," I told her, "He'll let us know soon as he finds something."

"Great," Isabella said, then sighed. "I hope Phineas is okay, wherever he is..."

"Me too," I agreed, sitting next to her next to the window. I didn't want to think of what could be happening to him. How long had he been gone? Until this morning, none of us had noticed anything different. Did that mean that he had been taken sometime last night? or that the monster had only _now_ made a noticeable mistake? I sighed, trying to push out of my head the thought of Phineas being injured, possibly dead. I had to believe that he was still alive. I wouldn't be able to take it if he wasn't.

My cell suddenly beeped, making me jump. I picked it up and said, "Hello?"

"Oh! Marissa," came Baljeet's voice from the other end, "I am afraid I have been unable to find out anything about this scary monster. I have failed terribly!" his voice was piercing and I thought I heard him crying for a moment. There was a small silence and then he continued. "I am sorry, Marissa, but I can be of no help."

At this my heart sank. If even Baljeet knew nothing about this monster, then who did? How would we defeat it? When could I see my li'l bro again? For now I just sighed, snapping the phone shut and turning glumly to Isabella and Candace. "Baljeet's got nothing," I told them, "Now what do we do?"

"What? Nothing?" Isabella exclaimed, turning to me and frowning. "That can't be right. Baljeet _always_ knows something."

I shook my head. "He doesn't have a clue."

Isabella's eyes fell, settling sadly on the floor. "Okay," she said quietly.

"Hey," I said, "We'll get Phineas back. Somehow."

"But how?" Isabella cried, suddenly angry, "Baljeet doesn't know anything!"

"Perhaps Moon does," Ferb said from the doorway, making us jump. "She seems knowledgeable in the supernatural."

"You know, you might be right," Isabella said reluctantly. I could tell she didn't like Moon, and she probably never would. Or maybe it was just me.

"I hope so," I sighed, "Why don't you go over to her house and ask her. With any luck she'll be of more help than Baljeet."

"Now wait a minute, why do _I_ have to go?" Isabella protested.

"Ferb'll go with you," I added, "Right, Ferb?"

Ferb only nodded.

"See? You two meet back up here in twenty minutes. Me and Candace'll keep an eye on that monster," I knew Candace would be doing most of the keeping-an-eye-on, but that was okay with me. Despite his resemblance to my brother, I didn't even want to _see_ that impostor. Whatever it had done to Phineas, I was going to make sure it would pay, but I also knew that if it had captured him it had some tricks up its sleeves. That, I suppose, is what scared me the most about it. How were we going to stop it? Hopefully Moon would know...


	5. Interrogation

Impostor

Chapter Five: Interrogation

Isabella

I didn't think it was fair that _I_ had to go out to Moon's house. Marissa knew I didn't like Moon. She should have gone herself. But maybe Moon _could_ help. Ferb had been right about her, although I didn't like to admit it. She had been pretty good at fighting those zombies when we'd first met. But I still didn't like her. She was too eager to destroy. I didn't want anyone around her getting hurt.

She lived in that old abandoned place at the end of the street. It was haunted and we all knew it, but somehow Moon seemed exactly like the kind of person who would fit the place. It was always raining there, even when the rest of town was sunny, and all the trees that lined the driveway were dead. The driveway itself wound through a small woods and led to a rusted iron gate. The name at the top read _Shadowshire_ and the mansion loomed behind it, casting a creepy outline against the sky. Most of the windows were broken and the winds howled ominously through the empty rooms, making my spine tingle a little. As I came closer, I noticed that the lawn was composed more of weeds than of grass, although it was still a dull brown instead of green. The two front doors were heavy oak, and one of them had an old brass knocker that neither me nor Ferb could reach. We stood at the door but still I was hesitant. I turned to Ferb and asked quietly, "Do I _have_ to do this?"

Ferb just gave me a blank look. Sometimes it seemed that those were the only kind of looks he ever gave.

I sighed. He was right, of course. "Fine," I formed a fist with one hand and pounded on the door, listening to it echo throughout the inside of the house. There was a silence, and then the door swung open. For some reason I had expected it to creak, but it didn't; instead stood Moon, easily twice as tall as me and very intimidating. She looked down on the both of us, and she seemed slightly amused. She raised one eyebrow for a moment and then said, "What brings you here?"

I wanted to tell her all about the unknown monster that had kidnapped Phineas, and how she had to help us, but instead I just squeaked. God, this was horrible. I tried again: "Moon, we-we need your help."

"With what?" Moon asked, with a neutral tone. I found it clear she was trying to make this last as long as she could. I hated that. I took a deep breath and then said, "There's a monster and it kidnapped Phineas. And we need you to find out what it is so we can defeat it."

"Monster?" Moon asked, "As in big and scary with lots of teeth and slimy claws and-"

"No, no," I said quickly, "Not-not like that. It looks like Phineas, but-"

"Then how do you know it isn't?" Moon interrupted, frowning a little. I knew she was doing this to be annoying, I just knew it. I gave her an irked look and then dug out the snapshot that Candace had caught. I shoved it into her hands, angry now, and snapped, "That's why. That's how we know, okay?"

Moon took the snapshot and gave it a quick look, turning back to me. "Now hang on a minute," she said skeptically, "Why should I help you with this? I'm gonna be risking my life here. These little buggers are trouble."

"If you don't help us then Phineas will probably die," I told her angrily, "How's that?"

"Not with your attitude," Moon shrugged, returning my angry look with her calm neutrality. Ooh, she was so irritating! Didn't she get it? Didn't she care that Phineas could _die?_

I would've given her a piece of _my_ mind, but before I could say anything Ferb reached into his pocket and puled out a wrinkled twenty-bill. He held it up to Moon and she gave him a brief look. She then took it and turned back to me. "It's called a soul-sucker," she told me, "It's got some weird Latin name too but that's not important. We better get back to your house so I can see how bad it is."

"Finally," I said, relieved, "C'mon," we went quickly down Moon's driveway and out of the rain that always plagued her house. I was glad to be out of it and we made our way back to the Flynn-Fletcher house. Since Ferb had come with us, 'Phineas' was working alone in the backyard. As soon as we opened the gate he turned to him and frowned. "There you are, Ferb. I was looking for you. What, do you need a leash or something? You gotta stop running off like that. Now c'mon. We gotta get this thing done before dinner so Mom can see it."

Ferb only nodded, ignoring the demeaning things that had been said about him. He gave the two of us a look and then followed him away into the backyard.

I turned to Moon. "You see?"

Moon gave a small yet elegant nod, but she remained completely reserved. Giving me a blank look she said, "Let's go inside. There's a couple of things I need to know."

We both went inside and up to Candace's room, where she and Marissa were waiting.

"About time you guys got back," Candace snapped, "Phineas-I mean, the monster looked like he was about to start breaking stuff."

"You must be Candace," Moon said, giving her a flat look.

"Yeah, what about it?" Candace turned to Moon and crossed her arms angrily.

"Nothing. Nothing at all," Moon replied. I could tell that Candace's attitude made her a little aggressive but she suppressed it, keeping herself neutral. Instead she just flopped back on Candace's bed, her hands laced behind her head and her eyes closed. "So, when did you first notice that your brother in fact may not have been?"

"Like just today," Candace said, "What does that have to do with it?"

"Everything," Moon replied smoothly. She seemed to be on her own agenda and didn't take Candace's irritability too hard. Instead she just asked, "Who first noticed?"

"Me-he forgot I was Jewish."

"I didn't even know that you were," Moon said, "But I take it that he has been aware of that for a while?"

I nodded. "Yeah, since I've known him."

"Anything else?"

"He was eating a zucchini like it was no big deal," I told her, "He hates zucchini."

"And both of these things happened today?"

"Yeah," I told her, "Come to think of it, that zucchini was from Missus Hirano's garden, which _you_ tore up trying to eat Ginger's rabbit."

Moon just shrugged. "You're welcome."

That irritated me, but I didn't say anything more. I knew that she didn't really have to be here and that if I ticked her off too much she might bail. So I bit my tongue, although I had plenty of things come to mind.

"So, what are we supposed to do?" Marissa asked, "I mean we have to do _something_."

Moon nodded. "Yeah, I'm working on it. See, soul-suckers are pretty tricky so you have to be careful with 'em."

"What else do you know about these things?" I asked a little suspiciously. I had a feeling Moon knew more than she let on and it would take another twenty bucks to get her to spill-which, unfortunately, I didn't have.

"Well, just the important stuff. They can only feed during the new moon and they're territorial, which means where there's one there's never more. They spy on their prey and then capture it and take its place, hiding the original away somewhere to eat during the new moon. They only do this just after eating their last catch so that they aren't caught. Like I said, tricky little buggers," Moon shrugged, her tone suggesting that perhaps she'd forgotten about us and was talking to herself.

"You mean Phineas is gone?" Marissa cried.

"No," Moon shook her head, "He's just hidden away somewhere. All we have to do is get that soul-sucker to tell. Since they're notorious for trickery we'll have to use force. I found a bunch of stuff in my new basement that I think might work, but it'll be up to you guys to get him to come over to my house. You know him better'n me. See if you can bring him over by dark. I'll be ready for him by then."

"Okay," Marissa took a deep breath and nodded. I could tell she was trying not to cry. So was I. I knew if I did Moon would think I was weak and I refused to give her another reason to pick on me.

"Great," Moon said, jumping up off the bed, "See you at dusk," she headed quickly out the door and a minute later Candace saw her jump over the gate with an apple in her hand.

"So how do we get that thing over there?" I asked, "We can't just tell it we're throwing a party or something."

"Maybe we can," Marissa pointed out. She frowned, thinking, and then turned back to me. "If we get all the kids in the neighborhood in on it, we can convince that thing to go and then Moon can take over from there."

"I can get all the Fireside Girls rallied up," I offered.

Marissa nodded. "Great. Tell them to make sure Phineas knows about the party at Moon's house. I'll go see how Ferb is doing."

"Okay," I nodded, a little more sure of the plan now. I left the house and went off to the Fireside Girls hideout to tell the rest of them about the plan.

It was after dinner and starting to get dark. 'Phineas' had bought the party idea and had said to tell Moon that he and Ferb would both be there. Moon and Marissa were waiting for him at Moon's house as Ferb, 'Phineas,' and I went up to the old place. Ferb pushed the gate open with a loud screech and we went up to the front door. Before he could knock it opened and Moon stood looking down on the three of us. "Come on in," she said, lingering on 'Phineas' for a moment. "You're early."

"Whoops, sorry," he gave an apologetic smile, but followed the rest of us into the house. "Whoa," he said, looking around at the empty rooms, "Nice house."

Even I had to admit that at one point the house could have been nice. The walls had been painted in a Victorian fashion and were decorated with ornate light fixtures. The floors were solid wood that made our footsteps echo throughout the room. Thick layers of dust and cobwebs covered everything, hanging like ghosts from the lights and making the place seem eery. There was no furniture here, and it made the room seem cold and dead. Just the kind of place Moon would think to live in, I thought to myself. Figures.

"This way," Moon led us down a rickety spiral staircase and down to what I assumed was the basement. It was bare stone, without decoration, and I could feel it getting cooler as we descended. We reached the bottom and I shivered, thinking to myself that I wouldn't be surprised if I had been able to see my breath. Moon didn't seem to notice, and instead led us into another room. It felt like a dungeon, with lit torches on the walls that made shadows dance across the room. There was a rack of tools along the far wall, as well as what looked like an autopsy table propped up like a coffin in one corner. The thought of it made me shiver again.

"Cool," came Phineas's voice, "Nice house."

Moon turned to him. "You like it?" she asked, taking a step closer.

"Yeah!" he enthused, "This house is awesome! All old and abandoned, and huge! Perfect for this party!"

"I'm glad you like it," Moon replied, suddenly grabbing him by the front of his shirt. "Coz you're not going anywhere for a while."

"What-hey!" he protested, "What's going on?"

"Take a wild guess," Moon growled, her demeanor shifting from neutral to angry. She shoved him roughly onto the table in the corner and tied him down with thick leather straps. Her voice was terrifyingly quiet and she gave him a hard glare. "A little bird told me you're a monster."

"What?" he cried, clearly panicked now. He pulled against the straps but it was clear he wasn't going to escape. "Who told you this? It's not true!"

"But it is," Moon snapped, leaning close to him and baring her teeth like a wild animal.

"No! No, I swear!" he frantically shook his head, flinching away from Moon's anger. He turned desperately to me and pleaded, "Isabella! Tell her it's not true! You know me!"

"Silence," Moon growled, turning to the rack of tools on the wall. She picked one of them, resembling something you'd expect to see in a mad scientist's lab. It was sharp on one end and Moon held it out to me. "You ratted him out," she said, "You want the first go?"

"What?" cried 'Phineas,' giving me a terrified look. "Isabella, y-you think I'm a monster?"

I couldn't say a word. I knew this wasn't Phineas. I'd seen those eyes-even though only in for a few frames of video-so I knew this was a monster, taking Phineas's place. But...he was staring at me, completely helpless, pleading, trembling a little. I knew, at least at some level, that this had to be done, but I wasn't heartless. I couldn't do it. I just couldn't. "I-I can't."

Moon just shrugged, turning back to the monster and giving him a coldly blank look, as if she was looking at something she'd scraped off the bottom of her feet.

"Isabella," the impostor pleaded, "Don't let her do this to me-you know I'm not a monster! Isabella!"

Slowly I shook my head. I knew this had to be done if we were going to get the _real_ Phineas back. I turned and started back toward the stairs. I didn't want to see this happen.

"No, please!" he cried, "Isabella-I love you!"

I stopped. I could feel my heart being crushed with those words, the words I've dreamed about for years. In my head I knew that Phineas hadn't said them, but in my heart I knew he had. Unable to keep them back any longer, hot tears welled up in my eyes and I knew he had hit me as hard as he could. But if he found out he'd broken me he'd be able to escape. I couldn't let him catch on to that. Finally I managed to choke out, "N-no-you don't."

Marissa put her hand on my shoulder reassuringly. "Come on," she said quietly, "Let's go home. We don't have to see this."

I just nodded. The two of us, followed by Ferb, went back up the rickety staircase, leaving Moon and that monster alone. I could hear his screams as we went out the door and they echoed in my mind all the way home. How could Moon do this? How could she just torture him like that? Even if it _wasn't_ Phineas. She hadn't hesitated at all. What was wrong with her? Didn't she have a heart? No, I realized, she didn't. It was then that I knew she was more dangerous than I had thought. Who was to say that she wouldn't kill Phineas herself? She had tried to once already. Why wouldn't she succeed this time? Phineas had told me, after the zombie incident, that they were now friends-but I knew they weren't. Moon didn't care at all for him; that much was clear. She'd only agreed to help us once Ferb gave her that twenty, and from that I knew she was only in this for herself. I only hoped that she was as good at dealing with this monster as she had been with the zombies.

The dark had become complete by the time I got home and I cried myself to sleep.


	6. Tricks

**A/N: sorry this took so long to update. I've had so much to do and so little time to do it. This is kind of a short chapter, but I'll have another one for you guys by the weekend.**

Impostor

Chapter Six: Tricks

Moon

It was nearly dawn by the time I had to take a break; the monster's screaming was starting to get to me and the last thing I needed was a headache. I was a little surprised at how easy it had been to catch - I had fully expected it to put up much more of a fight. They were usually more crafty than that. It hadn't told me where it had hidden Phineas, of course - I knew better than to think that would come so easily. It would probably take hours to get that monster to crack.

But it would crack. I'd make sure of that.

By the time I woke up, the dark of evening was beginning to set in and the sun had dipped between the trees past the front gate. I yawned and stretched, and then went back down to where the monster was tied. It had refused to change back to its normal form for me, although we both knew it could, and it had given me several less-than-pleasant remarks during the night. As I approached the basement I could hear it talking to itself, but as soon as I entered it was silent. It only glared at me with Phineas' eyes, one of which had bruised and was now almost black in color. After a minute it finally spoke. "You know I'll never tell you where your friend is," it told me, accompanied by an angry sneer.

I didn't answer. In the monster's presence I had to betray no feeling, no expression. If I did the creature would use it in any way that it could. Soul-suckers, I knew, were nefarious for their deceptions and trickery. Any scrap of weakness they could find was exploited and used for their own benefit. It was my job to give it no weakness. I couldn't. I'd been lucky Isabella hadn't cracked already, since the monster had hit such a nerve. It was obvious to me that she had a major crush on him - and that somehow he never seemed to notice under normal circumstances - but that wasn't much of an interest of mine. At this point, at least, I didn't care for any of them quite as much as they assumed I did. I knew Isabella didn't like me, although I guessed that was mostly because of how we'd met. I thought it likely that being covered in zombie blood didn't really make a good first impression. Phineas, on the other hand, had seemed attached to me almost from the start. He'd said we were now "friends," although I knew it would take some more time for that statement to become fully true. It was still a bit awkward for me here, since I'd been traveling for years and wasn't used to staying in a given place for more than a day or two. Something told me that it would be best if I left Danville behind, as I had so many other places. I was used to being a traveller and it suited me better anyhow. I hadn't even been certain of staying here, but Phineas had said that this house was abandoned, and that nobody wanted to come and bother me here. I didn't really mind it here, but I knew I would be more content on the move. But I couldn't go just yet - not when I still had business here. Speaking of business...

I turned back to the monster, in my hand now a rusty screwdriver, bloodied from last night's work. "Shall we, then?"

"No," said the monster, "Why bother? You'll just skip town later; you'll probably never see him again anyway..."

"Perhaps," I replied, keeping my voice even. I knew he was right - that after I left Danville and headed south, Phineas and the others would be little more than a blip in my life.

"Wouldn't it just be easier if you let me go? I won't go after you - I'm not a fool, after all."

"Easier?" I asked, "Probably. But I told them I would help them. I can't ignore that."

"And after you get out of here they wouldn't be able to tell either way," the monster looked up at me, and its voice was silky-smooth, as if it was stating truth instead of lies. It gave a tiny smirk and added, "I can play the part, you know. I already look it, don't I?"

"You do," I admitted reluctantly. I wasn't quite sure what point the monster was getting at - although I knew it went deeper than my urge to leave Danville - but I didn't want to give it the opportunity to finish. Instead I jammed the end of the screwdriver into the creature's ribs before it could make another comment.

The monster flinched in pain, but then looked back up at me. "Think about it," it said, "You'd never have to see me again. Unless you wanted. We could go together-"

"No," I snapped, jamming the screwdriver again into the monster's side.

This time the creature yelped, squirming away the little it could. Suddenly its eyes were meek, and its voice was cracked - a mimicry of Phineas's habits. "Moon, stop," it pleaded, "Just let me go."

I paused. I knew this creature was only a cruel mockery of Phineas - I knew it had hidden him away somewhere, and that it was my job to find him, and to bring him back to his family. I knew all of this, but...

I had only hesitated for a moment, but it was more than enough. The creature had me now, and we both knew it.


	7. The Clock is Ticking

**A/N: as promised, an update. After this it'll be a few more days before the next chapter, as I'm currently working on some things and hope to have them finished soon. Thanks to those who've been giving me all those good reviews; I promise to write again soon!**

Impostor

Chapter Seven: The Clock is Ticking

Ferb

I couldn't sleep. It was well past midnight, and I was pretty tired, but I couldn't keep my eyes shut - not while Phineas's bed across the room lay empty. I'd turned my back to it, to pretend he was there, but in my mind I knew better. I knew he was off somewhere, hidden away, likely hurt, and that he was scared, and that there was nothing I could do to help him. It was all in Moon's hands now. I could only hope he would be alive when she found him.

* * *

Eventually, morning came. Today was cloudy. It would probably rain later. I lay in bed, staring up at the ceiling, as I had been for hours, when the seven-o'clock alarm went off. I only let it ring.

* * *

It was almost nine by the time Candace came and shut off the alarm. She looked over at me and sighed, taking a seat on the edge of the bed. Her weight made her sink a little in the mattress.

"Ferb," she said gently, "Ferb, c'mon downstairs. Have some breakfast. You need to eat something, at least."

I knew she was right. My stomach had been growling since sometime last night. I hadn't had dinner because I was certain that if I did I'd be sick. I might be sick as it was, but I had to at least try to get something down - toast, maybe, or cereal. Toast sounded okay. I slowly sat up in bed and looked back over at Candace.

"C'mon, Ferb," she gave me a firm yet sympathetic look and put a hand on my shoulder. "You'll feel better if you eat something, I promise."

After a minute I nodded, and followed Candace downstairs to the kitchen. There was a half-empty box of cereal on the table and I slid into the empty chair next to it. Despite the fact that I was very hungry, I only had half a bowl, and by the time I was done the clouds had made the sky outside a hazy grey. The tree in the backyard was damp, and its leaves hardly made a sound as a slight breeze shuffled them around a little. Opening the back door I went out and sat under the tree, as I had done every day this summer, and sighed. It was always around this time that Phineas would start making plans for the day...but not today.

Today I was alone.

* * *

"Hey, Ferb."

I looked up to see Marissa coming out into the backyard. Her face was blank, but in her eyes I saw worry and sadness. She probably saw the same in mine. I moved over a little under the tree so she could sit next to me. She did, and when she spoke her voice was quiet. "You doing okay?"

Slowly I shook my head. I wouldn't be okay until I got my brother back. "I miss him."

Marissa sighed. "I do too...but there's nothing we can do about it. It's all in Moon's hands now."

I knew Moon could find him, but she was as much a curse as she was a blessing. I'd seen the flash of malice in her eyes when she'd met the impostor, and I'd seen how well she'd hidden it from him, so that he wouldn't suspect anything. That worried me a little, how well she could hide her thoughts, but it wasn't what concerned me the most. What concerned me the most was that she seemed to lack any sort of morals whatsoever. She couldn't tell between right and wrong - either she couldn't, or she simply chose not to. I hoped it was the former; at least then she could learn. As it was, she made me nervous. She was more interested in herself than the rest of us - although I couldn't blame her for that as she'd only known us for about a week - but at least she was relatively clean about that. I knew we were lucky to get her help regarding the impostor; if the twenty bucks hadn't been enough for her, even _I'd_ have begun to beg her for her help. That said, I understood her reluctance. She had mentioned how dangerous soul-suckers can be, and there was a significant risk for her as well. But we still had no clue what had happened to Phineas. I knew he was scared, alone, hurt...I only hoped he was still alive. I didn't want to think about what might happen if he wasn't.

It was hard enough not knowing. I was almost afraid to find out.

* * *

Eventually it began to rain. It started first as a light drizzle, but it escalated quickly into the beginnings of a storm. Marissa had gone back inside long before, but I hadn't moved. I only sat and let the rain come down on me. It didn't matter anymore - inside, outside, wet, dry, rain, sun...I missed Phineas and I couldn't be happy until I knew he would be alright. It was agony knowing that I couldn't help him, that there was nothing I could do for him. But I had to believe that at least he was still alive.

The gate to the backyard swung open with a creak, and before I could even think I looked up. "Phineas?"

No. Instead stood Isabella, wearing her raincoat against the coming storm. I could tell she had been crying - her face had turned a puffy red and there were still fresh tears around her eyes. She looked across the yard at me, then came over to the tree and stood over me. She spoke: "Ferb...how long have you been out here?"

I only shrugged. It didn't really matter anyhow.

Isabella softened. "Ferb, come on inside. Don't do this to yourself. I miss Phineas too, but..." her voice trailed off, and she took a deep breath so she wouldn't start crying again. After a minute of silence she looked back up at me, holding out one hand. "C'mon inside."

I stared at her hand for a moment and then took it, allowing her to lead me back into the house. Inside it was silent, save for the rain pattering on the roof, and I took a seat on the sofa in the living room.

Candace brought me a towel.

* * *

I didn't have dinner that night either. Instead I spent it in my room. I didn't want to see anyone, and I didn't want them to see me. Not until Phineas was back. I had to believe he would be.

There was a soft tap on the door and I looked up to see Marissa, the one person I could fully relate to right now. I knew the kind of bond she shared with Phineas - I was a bit jealous of it at times, but I could not say that I didn't share the same bond with him.

Marissa was silent as she came into the room and sat next to me on the bed. Her eyes met with mine for a moment, and then without a word she wrapped her arms around me, pulling me in close to her. After a moment I did the same. I could feel her shaking a little, but it wasn't until a small droplet landed on my collar that I realized she was crying.

"Ferb," she said quietly, in between sobs, "What if - what if he never comes back?"

I hesitated a moment, but then answered: "He will. He has to..."

"If he doesn't...would you sleep with me tonight?"

I only nodded.

"Thanks," Marissa's voice was barely a whisper, but in it was the tiny relief of a lost satisfaction, salvaged only by desperate hope. I wished I could be so lucky to share in that satisfaction - mine would only come with the return of Phineas.

Eventually I fell asleep, still in Marissa's arms.

* * *

It was dark when I awoke, and the clock on the bed-table read 12:23. It was still raining; occasional flashes of lightning lit the room, followed a few moments later by distant thunder. Carefully, I slipped out of sleeping Marissa's arms and tiptoed quietly to the window, staring out at the heavy rain. It seemed that the sky was crying for me - that it was crying for Phineas. I put my hand up against the cold glass, and it left a small foggy print where it had been. I could almost see Phineas's reflection staring back instead of my own. He stared back at me, but his face showed none of the pain I knew he must be going through, wherever he was...instead he only stared, blank-eyed, unblinking. I sighed. Brother, where are you? What has It done to you? Come home, Brother. Marissa needs you. _I_ need you...

It was an hour later when I returned to bed, slipping back in with Marissa for some more sleep. Her body was warm, and in her sleep she snuggled closer, draping one arm around me like a teddy-bear. She gave a sleepy murmur, and then was still for a moment until a sudden boom of thunder woke her. She sat up with a startled gasp, and then looked down at me. I put one arm around her, and gave her a comforting look.

Marissa took a deep breath, and then gave me a tiny appreciative smile. "Thanks, Ferb."

I only nodded as another flash of lightning lit the room.

"You think it'll rain all night?" she asked quietly, "You know it's hard for me to sleep during a storm."

I only shrugged. No sooner had I done that than the thunder following the lightning rumbled across the sky, making the floorboards shake a little. There was the distinctive squeak of the door opening, and I turned to see Perry waddle sleepily into the room. He hopped up onto the bed and immediately curled up between the two of us, gave a contented chatter, and fell asleep.

I thought maybe it would be best if I went back to sleep, too. I hadn't slept at all the night before, and I was exhausted. I settled back down, careful not to wake sleeping Perry, and Marissa did the same. I was about to close my eyes when another flash of lightning crossed the sky, leaving its jagged mark in the dark clouds, and in that brief moment of light, I could see, outside the window, what seemed to be a gargoyle, perched on the roof. But as the lightning faded I could see the distinct colour of glow-in-the-dark green, and I remembered Moon wore a pendant that colour on her choker. Thunder masked my bare footsteps as I ran to the window and pushed it open. The smell of rain greeted me as soon as I did, but my eyes were locked on Moon.

"Moon?" came Marissa's voice from behind me. "What're you doing here? and in the middle of the night, no less?"

Moon only gave a sly smirk. "C'mon," she said, "I know where your brother is."


	8. Rescue

Impostor

Chapter Eight: Rescue

Moon

"Where is he? Is he okay? Can I see him?" Marissa's words flew at me faster than I could process and I held up a hand to silence her.

"Follow me. Let's go get him," with that, I turned and jumped easily down from the roof, landing on my feet and glancing back up. I saw first Ferb and then Marissa come down after me as a sharp crack of lightning lit up the sky. The rain fell in thick sheets from the heavy clouds, and within a few seconds they were both soaked, but they didn't seem to care. Marissa brushed a stray clump of hair out of her face and then turned to me. Her voice was desperate when she spoke. "Is he okay...?"

I only shrugged. "Bellidor didn't say."

"Bellidor?"

"Yeah," I nodded, "That's what the monster seems to call itself..."

"Oh," Marissa shivered a little, pulling her wet pajamas closer around her as if it would help keep her warm.

"Come on," I told her, "Let's go find him."

"Okay..." although the rain made it impossible to tell for sure, I had a feeling there were tears in her eyes as she said this. She shivered, her wet pajamas clinging to her skin like sticky-tape and making her a sharply defined outline in the near-total darkness of the night.

I led them out of the backyard, to where Isabella was waiting - I'd woken her already since I had a feeling she wanted to meet Phineas again as well - and then the four of us headed out to the park. The creature had said that was where it had stashed Phineas away, and as soon as it had told me that I had left it to fetch the others. I knew they would want to see him, anyhow, and I didn't want to wait until morning either - the sooner Phineas got to go home the sooner I could kill Bellidor, since I didn't want it messing around with us again.

The park ahead lay quiet and empty, although a thin fog had begun to puddle in the low places, and I noticed Isabella clinging to Marissa. Her eyes darted about nervously, as if she expected something to come out of the fog and grab her. For good measure I poked her shoulder, watching in mild amusement as she jumped, squealing a little and then giving me a sour look. "Not funny, Moon."

I only shrugged, and then turned back to the cluster of trees where Bellidor had mentioned Phineas would be. As we came closer I spotted a rough boulder that had been slammed into the side of the hill, and I knew we were close. With the help of Marissa and Ferb the boulder was pushed aside, revealing a crude dug-out tunnel nearly a meter in diameter. Isabella immediately headed down to it but I held her back. "I'll go get him," I told her, "You wait here."

"But he's my best friend," Isabella protested, crossing her arms and giving me a significant pout.

I only shook my head. "No."

"Isabella, c'mere," Marissa took one of her hands and pulled her gently back, away from the tunnel, and held her comfortingly in both arms. She gave me an approving nod, and I turned back to the empty tunnel. As I disappeared inside, I could smell the distinct acidic environment that I knew soul-suckers preferred to live in. I knew that although Bellidor had lived here for a long time - years, decades, I couldn't tell for sure - he hadn't been here very recently. Days, perhaps, maybe more. Despite that, I knew Phineas was still alive. He had to be; Bellidor wouldn't be able to feed unless he was. The tunnel went deeper into the sodden earth, and the air inside was dank and musty. The pendant on my neck glowed, and although it only gave the tiniest bit of light, it was enough to allow me to see the way ahead. The tunnel split, and one of the side tunnels turned off into a small cavern. I turned down the tunnel and called, "Phineas?" My voice was quickly absorbed by the damp earth, and for a few moments there was only silence. But as I turned back to the other tunnel I heard a slight muffled yelp. Immediately I turned back, and followed the side tunnel into the more open space of the cave-room. The glowing pendant threw its tiny light onto the walls and in the back I could see him. He had been stuck firmly to the wall with hard mud, and there was a thick layer of it over his mouth, so that he couldn't speak. As soon as he spotted me his eyes locked on me, and he whimpered.

I put a hand on his shoulder, and looked into his eyes. When I spoke my voice was quiet. "Yeah, I'm here. You want to go home?"

With another whimper he nodded, tears forming in his eyes. He blinked them away, and one of them fell.

Without another word I took the knife from my belt, and its pointed tip chipped easily through the hardened mud holding Phineas back. As soon as he was free he collapsed, his arms wrapped tightly around my shoulders. He buried his face in my neck, and I could feel him shaking as he cried without a sound.

I immediately pushed him away, setting him down on the hard dirt floor as a shiver went down my spine. It wasn't that it was cold in here - it was really a bit warm, actually - but I didn't like anyone touching me. It just felt weird.

Phineas sat, almost dazed, on the floor. He looked up at me, shaking a little, and gave me a pathetic puppy-eyed stare.

I sighed. "Sorry," I said, "But I don't like things touching me. Marissa and Ferb and Isabella are waiting outside. You want to go see them?"

Phineas nodded, wiping the tears away from his eyes with the back of his wrist. "Thank you..." There was a relieved smile spreading across his face as he turned back toward the opening of the cave and disappeared into the tunnel, but after a minute there was a squeak, and I came out after him to see the creature with a strong hold on his throat. When he spotted me he smiled.

"How nice of you to join us," he said, his voice silky-smooth. His eyes traced mine, and after a moment of contemplation he spoke again. "I think it would be alright to stay here with him, if you'd like. You did come all this way to see him, after all."

Phineas pulled at Bellidor's grip, but it wouldn't let him go. His eyes darted to me and in them I saw only panic. "Moon-" he choked, "H-help me..."

"Quiet, you," Bellidor snapped. He glared back at Phineas, and he tightened his grip on his throat.

I drew my knife in one hand and advanced, growling a little. "Let him go."

Bellidor snorted, turning back to me. "Oh, is that what you think? That I'll just let him run free? It isn't that easy."

Without a word I attacked, tackling the monster and pulling it away from Phineas. He collapsed, coughing, to the floor, as I tried to pin the monster down. I glanced up to see him only briefly, but my eyes carried the urgency of life and death. "Phineas," I said, "Run."

Phineas didn't hesitate before turning to the open tunnel and scrambling away, out to where Marissa and the others were waiting. After he was gone I looked back down at Bellidor just in time for him to punch me square in the nose. I fell back, only briefly, but it was enough time for it to scramble up and after Phineas. Although it held his form it was quicker, and it made a wild grab for Phineas, catching his ankle and making him trip. It pulled him closer, and he shrieked, kicking frantically to make it let go.

"No!" I grabbed the impostor's collar, pulling it away from Phineas and shoving it back down the tunnel as we both scrambled back toward the opening. But the creature was fast, and it came after me, grabbing the back of my tank top and pulling me back. I retaliated with the sharp blade of my knife, leaving a wide slash in the monster's face, and kicked it back as I scrambled after Phineas toward the opening of the tunnel. I could see the dark night sky ahead, although after the total darkness of the tunnels it seemed almost like daylight. I could see Phineas's outline in it as well, making a mad dash for the night, and without looking back at the monster I followed him. But the monster had me again, grabbing me and pulling me back. As I tried to push it away it took the knife from my belt and held it menacingly in one hand. Despite only being Phineas's size it was very strong, and with one hand it took a hold on my throat. Its eyes narrowed in fury and it pressed the knife up against my skin. The blade was cold and sharp, and where it touched it left tiny lines of blood.

"You've made me lose him," it growled, its teeth bared like a wolf, "I might have to take you instead."

"No-" I pushed the monster away but it quickly pinned both my arms down, and its eyes were pure malice as it glared back at me. "Don't worry, I will kill you quickly, and I won't bother that little vermin..."

"Moon!" Phineas cried, and I glanced up to see him coming back down the tunnel after me. I quickly shook my head, giving him an urgent look. "No," I said, "Go-I'll handle this!"

"Well..." Bellidor's eyes settled again on Phineas, and it gave me the chance to give it a rattling headbutt that threw it off-balance and sent it back further down the tunnel. I snatched the knife from its hand before it could attack again, and the two of us scrambled back, out of the tunnel, into the night.

"Phineas!" Isabella exclaimed, immediately running up to him, "Oh my god!"

Phineas threw his arms around Isabella as fresh tears welled up in his eyes, although the rain quickly drowned them out. His voice was only a hoarse whisper, almost lost to the winds when he spoke. "I missed you..."

Marissa quickly went to Phineas, too, and Ferb as well, and the four of them converged in an enormous hug. The rain masked it but I knew they were all crying. But I wouldn't. I only stood back with a tiny smirk.

After a minute Ferb turned to me. He approached slowly, almost cautiously, but then wrapped both arms around me. "Thank you..."

Instinctively I wormed away from him, but then paused. When I looked down at him I could see the vast relief in his eyes, and I sighed. Cracking the tiniest smirk I replied: "You're welcome."


	9. Epilogue

Impostor

Epilogue

Phineas

At last I was home. I couldn't begin to tell you how I felt after spending who-knows-how-long in that dark place. Ferb and Marissa had taken me home while Moon and Isabella had gone back to theirs. Immediately we'd gone upstairs and Marissa had brought me several blankets to keep warm. I'd wanted to tell them how happy I was, that they'd come back for me, but they had both agreed that I should get some sleep, and that I could tell them everything in the morning.

And so I had.

* * *

I remembered everything the night Bellidor had taken me. It had been about midnight when something had woken me up. I'd assumed it had been Perry, since sometimes he wanders he house after dark, for whatever reason. I'd gotten up for some water, since I'd been thirsty anyway, but when I'd opened the door to the hall I'd seen a pair of glowing reptilian eyes staring back at me. My first thought had been that something had gotten into the house, and I'd been immediately concerned for Perry, since he was so small. But it had taken me instead. Even though this was over I could still almost see them sometimes at night, watching me.

I don't get up for drinks of water anymore.

* * *

The next day things began to return to normal, and for that I was relieved. Candace had even helped decide what it was we'd be building (we'd decided on an RC dilophosaurus) and when we were done we went over to Moon's house for dinner. I asked her what had happened - how they'd known to come and save me. Moon only said that Ferb and Isabella had come to her, and that she'd handled the monster when she'd caught it. She also said she'd sealed up the tunnels after she'd gotten me out so it wouldn't be after us again.

I was probably the most grateful for that.

* * *

I learned some things about Moon that night. Before, she had been reluctant to share much, but after this she said it was fair to tell us a bit more. She said she'd been traveling alone since she was seven, but she didn't want to talk about why she'd gone. She knew most everything about most everything supernatural, which was why she'd been able to handle the soul-sucker so easily.

I asked her why she didn't think of us as friends, even after this. She hadn't exactly said so, but I could see it was clear in her demeanor. She told me she'd only ever had one friend before, and that he'd betrayed her and tried to kill her. She said she might consider us friends eventually, given some time.

That was okay with me. I thought she'd make a good friend.

* * *

**Coming soon: **_**Duck Billed Crush**_


End file.
